IPC분류정보
국가/구분 |
United States(US) Patent
등록
|
국제특허분류(IPC7판) |
|
출원번호 |
UP-0573266
(2004-09-29)
|
등록번호 |
US-7796896
(2010-10-04)
|
우선권정보 |
GB-0322859.0(2003-09-30) |
국제출원번호 |
PCT/GB2004/004169
(2004-09-29)
|
§371/§102 date |
20060323
(20060323)
|
국제공개번호 |
WO05/034391
(2005-04-14)
|
발명자
/ 주소 |
- Sikora, Edmund S R
- Healey, Peter
|
출원인 / 주소 |
- British Telecommunications plc
|
대리인 / 주소 |
|
인용정보 |
피인용 횟수 :
12 인용 특허 :
93 |
초록
▼
A secure optical communication scheme uses differential delay D in an unbalanced Mach-Zehender interferometer to provide two copies of the optical source signal at a remote phase modulator separated in time by D. As D is much bigger than the coherence time source, the two copies of the signal are ef
A secure optical communication scheme uses differential delay D in an unbalanced Mach-Zehender interferometer to provide two copies of the optical source signal at a remote phase modulator separated in time by D. As D is much bigger than the coherence time source, the two copies of the signal are effectively uncorrelated. Both signals are phase-modulated by the remote sender's data and returned to the unbalanced interferometer. The phase modulator will be converted into amplitude modulation by the action of the interferometer.
대표청구항
▼
The invention claimed is: 1. A method of communicating between a first location and a second location, the method comprising: at the first location, generating output signals having an irregular component, and copying the output signals at least in part such that for each output signal, there is a
The invention claimed is: 1. A method of communicating between a first location and a second location, the method comprising: at the first location, generating output signals having an irregular component, and copying the output signals at least in part such that for each output signal, there is a pair of signal copies, the irregular component being common to each of the signal copies of a pair; transmitting, from the first location, each signal copy of a pair in a common direction over a common communications link; at the second location, mixing data onto the irregular component of a signal copy for at least some of the pairs of signal copies; and at the first location, receiving signal copies from the second location and, for pairs of received signal copies, combining the respective irregular components of the signal copies of a pair in order to extract therefrom data mixed at the second location, wherein the data is mixed at the second location such that between periods when data is being mixed, there are quiet intervals during which data is not being mixed. 2. A method as claimed in claim 1, wherein the source is an optical source, the output signals are optical signals. 3. A method as claimed in claim 1, wherein the mixing is carried out through modulation of the irregular component. 4. A method as claimed in claim 1, wherein the irregular component is random or pseudo random. 5. A method as claimed in claim 1, wherein the output signal has a waveform, the irregular component being the phase of the waveform, the waveform having randomly occurring phase changes. 6. A method as claimed in claim 5, wherein the irregular component is random or pseudo-random and the waveform has an average phase-coherence time of less than 10 pico seconds. 7. A method as claimed in claim 6, wherein the phase-coherence time is less than 1 pico second. 8. A method as claimed in claim 5, wherein the mixing occurs through phase-modulation of the waveform. 9. A method as claimed in claim 1, wherein signal copies of a pair are transmitted over the common communications link with a delay relative to one another. 10. A method as claimed in claim 1, wherein: signal copies are optical signals, differential delay being caused at an unbalanced interferometer, the interferometer having a first path and a second path, the transit time of the first path being longer than that of the second path, signal copies of a pair being caused to travel along a different respective path. 11. A method as claimed in claim 10, wherein the interferometer has a first coupling stage which is coupled to the source, the coupling stage being arranged to channel one portion of the incoming radiation intensity from the source along one path, and another portion of the incoming radiation intensity along the other path, so as to form the first and second signal copies. 12. A method as claimed in claim 11, wherein the interferometer has a second coupling stage for combining radiation from the first and second paths, and for coupling the combined radiation to the common communications link. 13. A method as claimed in claim 12, wherein the signals returned from the second location are each channeled along the first and second paths by a second coupling stage, and wherein the so channeled signals are subsequently combined at the first coupling stage. 14. A method as claimed in claim 1, wherein the source is configured to produce a continuous signal stream. 15. A method as claimed in claim 14, wherein the output signals have predetermined respective positions in the signal stream. 16. A method as claimed in claim 1, wherein the signal copies are delayed relative to one another at the first location, and wherein at the second location, signals are mixed according to a burst mode protocol, in which protocol the time between bursts is larger than the duration of the differential delay. 17. A method as claimed in claim 1, wherein the signals returned from the second location to the first location are returned along the common communications link. 18. A method as claimed in claim 1, wherein signals are reflected by reflector means at the second location in order to return the signals to the first location. 19. A method as claimed in claim 1, wherein the signals are modulated at the second location. 20. A method as claimed in claim 1, including monitoring the signals returned from the second location, so as to detect whether a physical disturbance in the communications link occurs. 21. A method as claimed in claim 1, wherein: for each pair of out bound signal copies transmitted from the first location to the second location, one copy is delayed such that there is a leading copy and a trailing copy, there being a differential delay between the leading copy and the trailing copy, and for each pair of signal copies returned from the second location, the leading copy is delayed at the first location, such that when the two copies are combined, the differential delay is reduced to allow the copies to be combined substantially instep. 22. A method as claimed in claim 21, wherein a trailing copy of a signal pair is delayed at the first location by a delay stage, a leading copy of the pair in the return direction being delayed by the same delay stage in order to reduce the differential delay between the two copies. 23. A method as claimed in claim 1, wherein to combine the signal copies of a pair, the signal copies are caused to interfere. 24. A method as claimed in claim 1, wherein the signal copies of a pair have a differential time delay associated therewith, and wherein the duration of the quiet intervals is greater than the differential time delay. 25. A method as claimed in claim 1, wherein the periods during which data is mixed are each shorter than the differential time delay. 26. A method as claimed in claim 24, wherein the periods during which data is mixed are each shorter than the differential time delay. 27. A method of communicating over a data link, the method comprising: generating output signals having an irregular component; copying, at least in part, the output signals such that for each output signal there is a pair of signal copies, the irregular component being common to each of the signal copies of a pair; transmitting at least one signal copy of each pair in a common direction onto a common communications link; receiving, from a remote location, returned signal copies previously transmitted to the remote location, the irregular component of the returned signal copies having data mixed therewith; and combining the received signal copy of a pair with the other signal copy of that pair, such that, in dependence on the combination of the respective irregular components of two signal copies of a pair, a data signal is generated, which data signal is indicative of data mixed remotely with the returned signal copy, wherein the data is remotely mixed such that between periods when data is being mixed, there are quiet intervals during which data is not being mixed. 28. A method as claimed in claim 27, wherein the delay is varied randomly or pseudo-randomly. 29. A method of communicating between a first location and a second location, the method comprising: at the first location, copying, at least in part, an output signal received from a source such that for each output signal, there is a pair of signal copies, an irregular component being common to each of the signal copies of a pair; transmitting, from the first location, each signal copy of a pair in a common direction over a common communications link; at the second location, applying data onto the irregular component of a signal copy of at least some of the pairs of signal copies; and at the first location, receiving signal copies from the second location and, for each pair of signal copies, combining the respective irregular components of the signal copies from that pair in order to extract therefrom data mixed at the second location, wherein the data is mixed at the second location such that between periods when data is being mixed, there are quiet intervals during which data is not being mixed. 30. A communications apparatus comprising: a source for generating output signals having an irregular component; a copying stage for copying, at least in part, the output signals from the source such that for each output signal, there is a pair of signal copies, the irregular component being common to each signal copy of a pair; a transmission stage for transmitting the signal copies of a pair in a common direction onto a common communications link; a receiving stage for receiving signal copies returned from a remote location, the irregular component of at least some of the returned signals having data mixed therewith; a combination stage for causing respective irregular components of the returned signals to combine; and data processing means coupled to the combination stage, the data processing means being configured to generate in use a data signal in dependence on a combination of the of the returned signals of a pair, the data signal being representative of data, if any, carried by a returned signal, wherein the data is remotely mixed such that between periods when data is being mixed, there are quiet intervals during which data is not being mixed. 31. Communications apparatus as claimed in claim 30, wherein a coupling stage is provided which acts (a) as the copying stage for signals travelling in an outbound direction towards the common communications line, and (b) as the combination stage for signals travelling in a return direction from the common communications link. 32. Communications apparatus as claimed in claim 31, wherein the copying stage and the transmission stage are connected by a first path and a second path, each of the first and second paths extending between the copying stage and the transmission stage, the transit time associated with the first path being greater than the transit time associated with the second path. 33. Communications apparatus as claimed in claim 32, wherein the paths are formed by an unbalanced interferometer, preferably an unbalanced Mach-Zehender interferometer. 34. Communications apparatus as claimed in claim 30, wherein the source is an optical source having a coherence time less than a differential delay associated with a first and second path. 35. Communication apparatus as claimed in claim 34, wherein the ratio of the differential delay and the coherence time of the source is at least 105, preferably at least 107.
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